I have heard about unpegged bracing but I did not know it was widespread. I cannot recall seeing an unpegged brace in northern New England. I have seen a barn where the braces were not flush with the outside face but held in around one inch. Sheathing boards are often nailed to the braces. Brace tenons are often 3 1/2" long to 4", always barefaced. Long braces are extremely rare in my experience. Peg materials I have seen are usually red oak but I just surveyed a barn with hexagonal pitch pine pegs and an ell with octagonal red maple pegs, both here in Maine.

Does anyone know how the framers of yesteryear decided to size there braces? Why 36" vs 42" vs 48" etc.

Thanks; Jim

HouseWright
I agree. I know there are different regional framing styles, but un-pegged braces is not something that I’ve seen often in the NE. This could be likened to the scarf over brace or scarf over post issue?

Timbo,
I think you’ll find that the brace mortise and tenon joint failure mode is controlled by the tenon relish. I believe that the research by Dick Schmict’s and other’s support this conclusion. Ed Levin has also written a few articles on the engineering implications of allowing braces to carry tension, and conversely not allowing the braces to carry tension. The problem with allowing the brace tenon joint to fail mathematically in tension or to carry no tension load or do to actual loading, is that the only other load carrying mechanism that is available is post bending and/or girder bending. We’ve tried to mathematically release the tension capacity of the brace and have had trouble accommodating the addition loading on the frame. There are obviously issues with trying to accommodate high tension loads on your typical brace arrangement.

I would like to hear how other engineers who participate in this forum handle this problem. This has been one of the most difficult TF engineering problems for me. I try to design what I consider ‘well braced’ buildings. I use lots of braces and ‘deep’ braces were I can, but the brace tension issue will not go away.

I’m not sure if there is a benefit of starting another thread in the TF engineering forum to further discuss this or continue here?

Thanks, pete

beerfreak, It seems to me it would also depend upon lay-out method which would depend on the wood. It seems that if the square rule method was used and thus housings had to be cut because of different dimensioned timbers it would make more sense to have the shoulder run to an outside face. It takes a lot less time to cut a housing for a brace if you can cut from an edge as opposed to cutting a housing with wood on each side of it. I'm no expert on tradtional barns but it seems that with the tools available it would have been a certain mess to center a brace in square rule without a router, instead run the brace to a face, handsaw, then chisel.

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[Originally posted by beerfreak:
I have decided to fit the braces in the centre [center] of the post and peg all the way through as the car port will be open,so walls or cladding do not apply.
I am looking at 6"x 2.5" braces curved and 30"x 30" from the corner of the post if you can visulise it,the height up to the wall beam is 8ft,do you think this size of brace will look in scale.]
Wow. There is a wealth of info on here I am trying to digest it all. The sizes of green oak are 7"by 7" posts and beams.

It is pretty easy to scribe a brace into a plane other than flush with reference, but I've not seen it done historically on this side of the Atlantic.

I've seen but one SR'd barn with centered braces, but it doesn't count, it was commisioned by a wealthy industrialist who returned to his hometown and was atypical from top to bottom. They achieved it by plowing the housing all the way across the face and it is ugly as sin.

If this thread morphed into a discussion on regional variation that might be interesting. I likewise have never seen an unpegged brace here in NNE. Have long tried to research why common purlins are dominant here, and most of the scarfs I know of fall over nothing whatever, but between the braces and are most often bladed abutments or believe it or not, are free tenons, long abbuting bridle joins and a chunk of plank

The (really old builders ) did take racking into account. Some used knee braces on the top of ties in addition to the commonly used ones below.

Another issue is the lenght of the brace and how that effects racking. There is a documented example of a 400+ yr old stucture in eastern NY. The corner posts have braces that extend nearly 3/4(!) the height of the post they are supporting, would you expect such a frame to rack (or not pass code for such...)? These braces extend from the sills to nearly the top of the posts. It withstood 400 years of all those "northeasters" until it was dismantled for restoration ..... where will the "stronger" stick built buildings be in 2300?

To quote the reference" Each corner post had two great braces from the tops of the posts to the sills, used to keep the wind from wrenching the frame" " They intersected with half lap joints the two outside wall girts--smaller cross beams between wall posts used to nail on boarding. There were in addition to the regular braces at the intersection of cross beams with posts throughout the frame. Between them they appeared to brace a fortress against wind and tide." R. Babcock

Don't sell timber frames short, and do not limit your designs to what you have "seen" (or read) is the current fad or design. I'm sure ther are yet stronger TF buildings that can be achived!

P.S. Have seen many unpegged knee braces here in New England on buildings standing (still)

Bracing from post to sill has been a long or standard situation in Europe. And you'll see it here in New England also:



The reasoning behind this placement of down braces, sometimes called standing braces is that it transfers the wind load directly to the sill/foundation near the point of the load.
For standard "hanging braces" the wind load has to be transfered over to the opposing brace (that works in compression). Sometimes this opposing brace is several bays or aisles away. This means the entire frame is wrenched, wracked or shifted until the compression brace resists it.
A standing or down braces prevents this from happening by absorbing the load at the wall were it is being applied.
In a barn or outbuilding this whole frame racking won't matter that much, but a house with sheet rock could see some cracks or other evidence of the racking if it was pushed to extreme....

Jim Rogers

Jim, A very nice example. Thanks!!!

On corner posts the racking effect can better be transmitted by truely long braces ( ca. 2/3-3/4 post height) otherwise the post holds the load above the brace. This is not always pactical in middle bents (except lenght wise along the sills) as the braces would extend into the structure's interior (O.K. if thats going to be an interior wall...) and complicates joinery by requiring a halflap at any bents inersected. Still it is a feature many ignore as a way to make a building more immune to racking.

That's why the German design uses long braces going down instead of cute little braces between post and tie beams that do little.